It is known to transmit Power over Data Lines to remote power equipment. Power over Ethernet (PoE) is an example of one such system. In PoE, limited power is transmitted to Ethernet-connected equipment (e.g., VoIP telephones, WLAN transmitters, security cameras, etc.) from an Ethernet switch. DC power from the switch is transmitted over two or more twisted wire pairs in the standard CAT-n cabling. One or more of the wire pairs also transmit differential data signals, since the DC common mode voltage does not affect the data. In this way, the need for providing any external power source for the Powered Devices (PDs) can be eliminated.
A newer technology is Power over Data Lines (PoDL) where power is transmitted over a single, twisted wire pair along with the differential data. As of the date of this disclosure, the IEEE is in the process of developing a standard for PoDL as IEEE 802.3bu. PoDL may be more flexible than PoE and, since it requires just one wire pair, is likely to become a popular technique, especially in automobiles.
In the example of using PoDL in automobiles, there may be a temporary short to ground, or to a battery voltage, or between the wires due to automobile vibrations or other causes. During the short, the PoDL or Ethernet communications may be interrupted. Without any protection circuitry, the short may destroy the PoDL components, result in excessive heat being generated, or disable an important feature of the automobile.
What is needed is a circuit architecture to detect such faults to suspend operation of the PoDL system and then quickly resume normal operation if the fault is removed.